As the subject says, do infantry with the dismountable trait count as cavalry or infantry for the purposes of how many red cards you need for a flank march?
As written there is no mention that they are treated differently from any other Infantry.
This does seem a tad wrong IMO and maybe we can bend/expand the "move as formed cavalry/camelry when mounted" part to include when on flank marches to allow them to arrive on 2 Reds as long as they do so mounted.
It certainly seems like mounted infantry should have an advantage coming in from the flank. It could even be argued to be one of the main advantages.